Many water power systems, in particular floating systems, cannot handle storm waves. Systems operating with large area panels perpendicular to the propagating direction of waves are susceptible to huge anchoring forces. Further, systems which make use of anchoring forces in order to produce energy, so-called point absorbers, as well as systems that depend on buoyancy bodies, have problems related to end stops.
It is known that not only the energy of the linear waterflow, but also the waterflow energy of waves, may be used for producing electricity as disclosed in the following documents:
WO 02/44558 A1 (Rossen) [0005] U.S. Pat. No. 6,036,443 A (Gorlov) [0006] DK 171714 (Stenberg) [0007] DE 102004060275 A1 (Jobb)
In addition, WO 2008/093037 A1 discloses an apparatus wherein blades impart rotation of a main body in response to a flow of fluid such that angular momentum of the main body is conserved upon a change of direction of fluid flow.
Systems that are driven by rotors are not as susceptible to faults related to end stops as non-rotor systems. The known rotors that are driven by the waterflow energy of waves are often based on stationary vertical drive shafts which transfer the rotational energy to a generator arranged above the water level outside the rotors. According to such systems, a pole is anchored to the seabed in order to absorb the counteracting torque related to the stator of the generator and to absorb the counteracting torque related to large axial and radial forces originating from long radial rotor blades. However, such systems are only for use in shallow waters. Further, since large forces related to storm waves are not easily handled by rotors having long rotor blades, an additional mechanism for protection of the system is needed, such as a mechanism for adjusting the height of the rotor and for retracting the blades.
Also known in the prior art are floating systems having a vertically orientated drive shaft in relation to counteracting torques of the stator of a generator, which drive shaft may be provided with rotor units rotating in opposite directions. In such systems, large axial damping panels can be arranged, e.g. 40 meters beneath sea level, which implies that the systems are for use only at locations where the ocean reaches great depths, such as more than 40 meters.
The efficiency of rotors having a vertical rotation axis is highly dependent on the position of the rotors with respect to the sea level, since the waterflow decreases exponentially with the distance from the water surface. Therefore, in relation to a pole mounted rotor system, a sufficiently large water depth, or an option for adjusting the position of the rotors with respect to the water level, is needed due to variations of the water level and variations of the wave amplitudes.
Rotor systems, which are adapted to take advantage of waterflow energy and having a horizontally orientated rotational drive shaft, are also known in the prior art. Such systems are rotationally supported in bearings in associated floating members, however, significant expenses and considerable maintenance is required in order to withstand the forces that are formed in the bearings.
In one of the prior art documents, the fabrication costs are sought to be reduced by considerable reduction of the diameter of the rotor. Further, in order to achieve a high energy conversion efficiency, many rotors are placed closely in parallel, with two associated generators, in a floating arrangement. Such arrangements have low operational reliability in particular due to floatsam.
To overcome the mentioned difficulties, it is an object of the invention to provide an improved rotating apparatus for harnessing the power of waterflow, in particular the power of water waves and the power of the linear waterflow, so that the above mentioned disadvantages are eliminated or reduced.